Tests are today an essencial part of the software development. They help us to minimize the number of bugs. They ease the verification that everything keeps working after code refactoring or changes. And also, among other things, they give confidence to the team, as they can be an indicator of the status of the project. There are many different types of tests: integration tests, unit tests, load tests… This entry will be focused on unit tests in JavaScript and how to use Sinon to get rid of the dependencies from another modules. We will be able to run these tests with Mocha as we saw previously